Please explain in detail what each part of the code does to get the outcome

NA = 1 2 3 4 4 def decryption(key, message): message message. upper() alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" result = print(key) for letter in message: if letter in alpha: letter_index (alpha.find(letter) - key) % len(alpha) 5 6 7 8 00 result = result + alpha[letter_index] else: result = result + letter return result 9 10 11 12 13 14 15 16 17 18 19 def main(): filename = "ceaserEncrypted.txt" ceaser_list = [] # file reading with open(filename) as file_in: ceaser_list [] for line in file_in: ceaser_list.append(line) 20 21 22 23 24 25 = 26 27 decrypted_list [] # store key key = int(ceaser_list[@]) # decrypt every message for message in ceaser_list[1:]: decrypted decryption(key, message) decrypted_list.append(decrypted) 28 29 30 31 32 33 34 35 36 37 # make output file file1 = open("ceaserDecrypted.txt", "w") = # write to output file for mesage in decrypted_list: file1.write(mesage) 38 39 40 main()